Apparatus for processing a defect in an optical disc apparatus

ABSTRACT

An apparatus for processing a defect includes a defect detection unit and a main filter. The defect detection unit detects a presence of a defect in a disc, and when the defect is detected, outputs a reset signal to the main filter. The main filter receives a focus error signal or a tracking error signal, which are digital signals, and outputs a focus regulation signal or a tracking regulation signal to regulate a focus or a tracking location of the disc by filtering the focus error signal or the tracking error signal. The reset signal is applied to the main filter and resets the signal values of a high-frequency component existing in the main filter to 0. Using the apparatus, a peaking phenomenon of the focus regulation signal or the tracking regulation signal can be removed and, accordingly, an accurate servo filter characteristic can be obtained.

CROSS-REFERENCE TO RELATED PATENT APPLICATION

This application claims the benefit of Korean Patent Application No.10-2006-0130838, filed on Dec. 20, 2006, in the Korean IntellectualProperty Office, the disclosure of which is incorporated herein in itsentirety by reference.

BACKGROUND OF THE INVENTION

1. Technical Field of the Invention

The present disclosure relates to an apparatus for processing a defectin an optical disc apparatus and, more particularly, to an apparatus forprocessing a defect that generates a tracking regulation signal or afocus regulation signal when a defect is present on the surface of adisc installed in an optical disc apparatus.

2. Discussion of Related Art

In an optical disc system, data is written and read along a grooveformed on a surface of a disc, that is, along a disc track on thesurface of the disc. A head reads the rotating disc and amplifies aradio frequency (RF) signal and then generates a tracking error (TE)signal using the amplified RF signal. Then, a tracking regulation (TRO)signal is generated using the generated TE signal to regulate andcompensate for any tracking error.

Also, while reading the data by irradiating light on the rotating disc,focusing of the irradiated light on the disc should be regulatedperpendicularly to the disc surface. Hence, a focus error (FE) signalincludes information about whether the focusing is correctly adjusted ornot. Then, a focus regulation (FRO) signal is generated using the FEsignal to regulate and compensate for the focusing of the irradiatedlight on the disc.

Accordingly, an apparatus for processing a defect, which receives the FEsignal or the TE signal, and generates the FRO signal and the TRO signalin order to track the desired disk track and to adjust the focusing ofthe irradiated light on the disc is required.

FIG. 1A illustrates a conventional apparatus 100 for processing a defectin an optical disc apparatus.

Referring to FIG. 1A, the conventional apparatus 100 for processing adefect in an optical disc apparatus includes a DC hold filter 101, adefect detection unit 103, a switching unit 110, a focus/tracking mainfilter 120, and a digital to analog converter (DAC) 105.

When a defect is present on the surface of the disc, the defectdetection unit 103 detects the defect and outputs a defect controlsignal D_CON. In this example, the defect indicates the presence of afingerprint adhered on the surface of the disc, a contaminant adhered onthe surface of the disc, a groove on the surface of the disc, a scratchon the surface of the disc, or the like.

If the defect exists on the surface of the disc, the reading of data mayfail as performed by a read signal (RF signal) generated by an opticalpickup (not shown) while reproducing the disc (reading the data), andthe controlling capability of a servo controlling the tracking, thefocus, and the like, may deteriorate. Accordingly, when the defect ispresent on the surface of the disc, the defect detection unit 103immediately outputs the defect control signal D_CON in order to processthe defect of the conventional apparatus 100.

When the defect control signal D_CON is applied to the switching unit110 after the defect control signal D_CON is activated to logic high,the DC hold filter 101 outputs a uniform value so as to output the FROsignal or the TRO signal as uniform values. Hence, a fixed DC value isheld and then outputted from the DC hold filter 101 to thefocus/tracking main filter 120. Here, the fixed DC value is a signalhaving a low frequency.

When the defect control signal D_CON is applied to the switching unit110 as logic high, the switching unit 110 transmits an output signalOut_DChold of the DC hold filter 101 to the focus/tracking main filter120 in response to the applied defect control signal D_CON. Before thedefect is present, the switching unit 110 is connected to an L terminalso as to input the FE signal or the TE signal to the focus/tracking mainfilter 120.

The focus/tracking main filter 120 receives and filters the FE signal orthe TE signal in order to output the FRO signal or the TRO signal,which, regulate the focus or tracking position of the head on the disc.

The focus/tracking main filter 120 includes a high-frequency gain filter122 and a low-frequency gain filter 124.

The FE signal and the TE signal are digital signals converted fromanalog signals. Accordingly, an analog to digital converter (ADC) (notshown) is installed in front of the input ports of the FE signal and theTE signal.

The high-frequency gain filter 122 of the focus/tracking main filter 120receives the FE signal and the TE signal and outputs the FE signal andthe TE signal after filtering the high-frequency components of the FEsignal and the TE signal. In this case, the high-frequency components ofthe FE signal and the TE signal are at 500 Hz or more, that is, a signalfiltered from a frequency band that is required to be amplified by auser. The high-frequency gain filter 122 is not a high-pass filter(HPF), however, the high-frequency gain filter 122 has thecharacteristics of a bandpass filter (BPF), in other words, not allsignals in a certain frequency or more are filtered, however, signals ina frequency band, which a user desires to filter, are filtered.

The high-frequency gain filter 122 filters a signal in a relativelyhigh-frequency band f_h. In this case, the relatively high-frequencyband f_h that is to be filtered can be set differently according to anapparatus used or a user and, thus, the relatively high-frequency bandf_h is not limited. The high-frequency components filtered and outputtedfrom the high-frequency gain filter 122 are an AC component signal.

The low-frequency gain filter 124 receives the FE signal or the TEsignal and outputs the FE signal or the TE signal after filtering thelow-frequency components of the FE signal or the TE signal. In thiscase, the low-frequency components of the FE signal or the TE signal area signal at 100 Hz or lower, that is, a signal filtered from a frequencyband that is required to be amplified by a user.

The low-frequency gain filter 124 has characteristics of a low-passfilter (LPF). Accordingly, a signal in a relatively low frequency bandf_1 or below is filtered and then outputted from the low-frequency gainfilter 124. In this case, the low-frequency band f_1 that is to befiltered can be set differently according to an apparatus used or a userand, thus, the low-frequency band f_1 is not limited. The low-frequencycomponents passed by the low-frequency gain filter 124 are a DCcomponent signal.

An adder 126 adds an output signal O_HF of the high-frequency gainfilter 122 and an output signal O_LF of the low-frequency gain filter124 and then outputs the result. Accordingly, an output signal of theadder 126 is a signal resulting from the addition of the DC componentsignal in the low-frequency hand f_1 and the AC component signal in thehigh-frequency band f_h.

The DAC 105 outputs each FRO signal and TRO signal by converting thesignal outputted from the adder 126 to an analog signal through thedigital to analog converter (DAC) 105.

Hereinafter, the operations of the conventional apparatus 100 will bedescribed with reference to FIGS. 1B, 2A, and 2B.

FIG. 1B is a diagram illustrating the DC hold filter 101 used in theconventional apparatus 100 illustrated in FIG. 1A.

Referring to FIG. 1B, the DC hold filter 101 includes a plurality ofamplifiers 151, 153, and 155, an adder 157, and a filtering device 159.

The DC hold filter 101 receives the FE signal or the TE signal andoutputs the received FE signal or the TE signal after filtering very lowfrequency band components (the DC component) of the FE signal or the TEsignal. Since the DC hold filter 101 filters the DC components of the FEsignal or the TE signal, roughly uniform fixed values are continuouslyoutputted from the DC hold filter 101. Conventionally, the output signalOut_DChold of the DC hold filter 101 may be a fixed DC value of 0.

Hence, K20, K21, and K22 are the respective amplifier gains of theamplifiers 151, 153, and 155. The adder 157 adds an output signal of theamplifier 151 and an output signal of the amplifier 153 and then outputsa result. The filtering device 159 performs a filtering process on acertain frequency band and corresponds to a capacitor of an analogfilter.

The overall operation principles of the DC hold filter 101 are describedin U.S. Pat. Nos. 6,693,521 and 5,682,307. Also, the constitutions andoperations of the DC hold filter 101 are well known to one of ordinaryskill in the related art and, thus, detailed descriptions thereof willbe omitted.

FIG. 2A is a diagram illustrating the characteristics of each filter ofthe conventional apparatus 100 of FIG. 1A that is used for processing adefect.

The first graph 210 of FIG. 2A illustrates a frequency response curve ofthe high-frequency gain filter 122. In the first graph 210, signals in acertain relatively high-frequency band between the frequencies f_h1 andf_h2 and having a frequency f_h as a center are filtered. Thehigh-frequency gain filter 122 outputs signals having frequenciesbetween the frequencies f_h1 and f_h2 of the relatively high frequencyband and filters signals below frequency f_h1 and above frequency f_h2.

The second graph 220 of FIG. 2A illustrates a frequency response curveof the low-frequency gain filter 124. In the second graph 220, signalsabove a relatively low frequency band of a frequency f_1 are filtered.The low-frequency gain filter 124 outputs signals having a frequencyless than or equal to the frequency f_1 and filters signals havingfrequencies above f_1.

The third graph 230 illustrates a signal output from the adder 126. Inthe third graph 230, the signal in which signals illustrated in thefirst and second graphs 210 and 220 are added is outputted. The signaloutputted from the adder 126 has both high-frequency components andlow-frequency components.

The fourth graph 240 illustrates the FRO signal and the TRO signal,which have passed through the adder 126 and have already been convertedinto analog signals through the DAC 105. In a signal output from theadder 126, a high-frequency component signal 242 and a low-frequencycomponent signal 244 coexist.

FIG. 2B illustrates signals outputted from the apparatus 100 of FIG. 1Aused for processing a defect.

Referring to FIG. 2B, a disc is read for a track section from a to bhaving a defect, for example, a finger print, a contamination, or ascratch.

An RF signal is generated by an optical pickup from a rotating disc. Thegenerated RF signal having a uniform frequency indicates that the discdoes not have a defect, and the RF signal is regularly generated andoutputted. When a defect is present on the disc, the RF signal cannot begenerated and there is a gap during a section 252 of the RF signalindicating the presence of a defect.

The defect detection unit 103 detects that the track section from a to b(or a time when reading the track) has the defect, and outputs thedefect control signal D_CON activated as logic high during the tracksection from a to b having the defect. A signal DEFECT is a signalindicating the presence of the defect. Accordingly, the signal DEFECThas the same signal form as the defect control signal D_CON.

When the defect is present on the disc, a switch of the switching unit110 is switched to an H terminal and an output terminal of the DC holdfilter 101 is connected to an input terminal of the focus/tracking mainfilter 120, whose input signal is called FE1/TE1 and, thus, the signalFE1/TE1 during the track section from a to b having the defect isoutputted from the DC hold filter 101 as a fixed value 254. Accordingly,discontinuous points 256 and 258 occur in the signal when the defectoccurs and respectively end at discontinuous occurrence points a and b.

The focus/tracking main filter 120 is formed as a LPF and a BPF. Basedon the characteristics of a filter in terms of when the LPF and the BPFreceive the discontinuous signal from the DC hold filter 101, a peakingphenomenon occurs. Accordingly as illustrated in FIG. 2B, the FRO signaland the TRO signal reach peaks at the discontinuous occurrence points aand b. For reference, the DC hold filter 101 outputs a signal having aDC component having a uniform value with a very low frequency component.

As described above, the conventional apparatus 100 for processing adefect prevents a wrongful tracking and regulates a focus by connectingthe output of the DC hold filter 101 to an input terminal of thefocus/tracking filter 120 when the defect is present. The discontinuouspoints a and b that occur in the signal inputted to the focus/trackingmain filter 120, however, cannot be removed. Accordingly, the peakingphenomenon of the FRO signal or the TRO signal at the discontinuouspoints a and b cannot be prevented. When the peaking occurs, thetracking or the focusing cannot be correctly regulated. In other words,the tracking may be inaccurately performed and the focus of the lightbeam cannot be accurately adjusted.

SUMMARY OF THE INVENTION

Exemplary embodiments of the present invention provide an apparatus forprocessing a defect, the apparatus has a simple constitution, is able tooperate stably by removing a peaking phenomenon, and can accuratelyregulate tracking or focusing.

According to an exemplary embodiment of the present invention, there isprovided an apparatus for processing a defect, the apparatus including:a defect detection unit that detects a defect in a disc, and when thedefect occurs, outputs a reset signal to a main filter; and the mainfilter that receives a focus error signal or a tracking error signal,which are digital signals, and outputs a focus regulation signal or atracking regulation signal to regulate a focus or a tracking location byfiltering the focus error signal or the tracking error signal, whereinthe reset signal resets signal values of a high-frequency componentexisting in the main filter to 0.

The main filter may reset the signal values of the high-frequencycomponent to 0 when the reset signal is applied thereto, and output thefocus regulation signal or the tracking regulation signal after removingthe high-frequency component of the focus error signal or the trackingerror signal.

The main filter may include: a high-frequency gain filter that filtersthe focus error signal or the tracking error signal to have ahigh-frequency gain and then outputs the filtered focus error signal orthe tracking error signal; a low-frequency gain filter that filters thefocus error signal or the tracking error signal to have a low-frequencygain and then outputs the filtered focus error signal or the trackingerror signal; and an adder that outputs the focus regulation signal orthe tracking regulation signal by adding an output of the high-frequencygain filter and an output of the low-frequency gain filter.

The apparatus may further include a digital to analog converter (DAC)that receives the focus regulation signal or the tracking regulationsignal from the main filter and then outputs the focus regulation signalor the tracking regulation signal after converting the focus regulationsignal or the tracking regulation signal to an analog signal.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the present invention will be understood inmore detail from the following descriptions taken in conjunction withthe attached drawings, in which:

FIG. 1A is a drawing illustrating a conventional apparatus forprocessing a defect in an optical disc apparatus;

FIG. 1B is a diagram illustrating the DC hold filter installed in theconventional apparatus illustrated in FIG. 1A;

FIG. 2A is a diagram illustrating characteristics of each filter of theconventional apparatus, as illustrated in FIG. 1A, for processing adefect;

FIG. 2B illustrates signals outputted from the conventional apparatus,illustrated in FIG. 1A, for processing a defect;

FIG. 3 is a diagram illustrating an apparatus for processing a defect,the apparatus included in an optical disc apparatus according to anexemplary embodiment of the present invention;

FIG. 4A is a diagram illustrating a high-frequency gain filter of theapparatus illustrated in FIG. 3 in detail, according to an exemplaryembodiment of the present invention;

FIG. 4B is a diagram illustrating a low-frequency gain filter of theapparatus illustrated in FIG. 3 in detail, according to an exemplaryembodiment of the present invention; and

FIG. 4C is a diagram illustrating signals outputted from the apparatus,as illustrated in FIG. 3, for processing a defect, according to anexemplary embodiment of the present invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The attached drawings for illustrating exemplary embodiments of thepresent invention are referred to in order to gain a sufficientunderstanding of the present invention, the merits thereof, and theobjectives accomplished by the implementation of the present invention.

Hereinafter, the present invention will be described in detail byexplaining exemplary embodiments of the present invention with referenceto the attached drawings. Like reference numerals in the drawings denotelike elements.

FIG. 3 is a diagram illustrating an apparatus for processing a defect,the apparatus included in an optical disc apparatus according to anexemplary embodiment of the present invention.

Referring to FIG. 3, the apparatus 300 includes a defect detection unit301 and a main filter 310.

The defect detection unit 301 detects a defect present on the surface ofa disc from the reflected light beam Sum_mainbeam signal and outputs areset signal S_RESET. The logic level of the reset signal S_RESET may belogic high or logic low according to the settings of a user.

The main filter 310 receives a focus error (FE) signal or a trackingerror (TE) signal as a digital input signal, filters the FE signal orthe TE signal in order to output a focus regulation (FRO) signal or atracking regulation (TRO) signal respectively regulating a focus of alight source or a tracking of a track in the disc.

In an exemplary embodiment, the FE signal or the TE signal generated asan analog signal should be inputted to the main filter 310 as a digitalsignal. Accordingly, although not illustrated, an analog to digitalconverter (ADC) is installed at a front terminal (an input terminal) ofthe main filter 310.

The high-frequency gain filter 312 receives the FE signal or the TEsignal and outputs the FE signal or the TE signal after filtering ahigh-frequency component of the FE or TE signals. In an exemplaryembodiment, the high-frequency component is a signal at 500 Hz orhigher, and the signal is selected from a frequency band that a userdesires to amplify. The high-frequency gain filter 312 only passessignals in the frequency band that the user desires and has thecharacteristics of a bandpass filter (BPF).

The low-frequency gain filter 314 receives the FE signal or the TEsignal and outputs the FE signal or the TE signal after passing alow-frequency component of the FE or TE signals. In an exemplaryembodiment, the low-frequency component is a signal at 100 Hz or lower,and the signal is selected from a frequency band that the user desiresto amplify.

An adder 316 adds and outputs signals O_HF and O_LF respectivelyoutputted from the high-frequency gain filter 312 and the low-frequencygain filter 314.

A digital to analog converter (DAC) 320 converts a signal outputted fromthe adder 126 to an analog signal, and outputs a focus regulation (FRO)signal and a tracking regulation (TRO) signal.

In an exemplary embodiment, the reset signal S_RESET resets the signalvalues of the high frequency component that is passed by thehigh-frequency gain filter 312 to 0 or a certain offset value. Morespecifically, the reset signal S_RESET resets the signal values of thehigh-frequency component that pre-existed in the high-frequency gainfilter 312 including the high-frequency component of the FE signal orthe TE signal in the high-frequency gain filter 312 to 0 or to apredetermined offset value. Generally, filtering devices in a digitalfiler can be expressed as Z⁻¹ with values of k*(1/jw). Such filteringdevices in the digital filter correspond to capacitors in an analogfilter. Accordingly, the signal components in the digital filtercorrespond to values of the voltages at both ends of the capacitors.

The signal values of the high frequency component are reset to 0 inorder to remove the signal values of the high-frequency component insidethe high-frequency gain filter 312. Also, the signal values of thehigh-frequency component are reset to the predetermined offset value inorder to adjust the initial values stored in the filtering devices to auniform value. When the signal values of the high-frequency componentare reset to the offset value, a signal can be detected by extractingthe offset value during an input and output. For example, when theoffset value is 3 V and the output is 5 V, the actual output value is 2V.

A signal generated due to a defect in the disc has at least hundreds ofHz in terms of frequency. Conventionally, the signal generated due tothe defect in the disc has a frequency between 1 Khz to 10 Khz.

Only the signal values in the high-frequency gain filter 312 are resetbecause a signal component converted due to the defect in the disc isthe high-frequency component of the FE signal or the TE signal.Accordingly, when the high-frequency component of the FE signal or theTE signal is converted and inputted to the main filter 310 due to thedefect in the disc, the signal components in the high-frequency gainfilter 312 are reset to 0000 (zero) and then outputted. Accordingly, anaccurate FRO signal or TRO signal can be outputted in spite of thedefect in the disc.

The low-frequency component of the FE signal or the TE signal is notrelated to the presence of the defect in the disc and, thus, does notchange. Accordingly, the low-frequency gain filter 314, which outputsthe low-frequency component of the FE signal or the TE signal, does notneed to be reset.

The adder 316 removes the high frequency component of the FE signal orthe TE signal that is undesirably generated due to the defect in thedisc, and only outputs the low-frequency component of the FE signal orthe TE signal that are to be correctly output.

FIG. 4A is a circuit diagram of the high-frequency gain filter 312illustrated in FIG. 3, according to an exemplary embodiment of thepresent invention.

The high-frequency gain filter 312 includes a plurality of filteringdevices 401, 403, and 405, a plurality of adders 411, 413, and 415, anda plurality of amplifiers 421 through 428.

As described above, the filtering devices (Z⁻¹) 401, 403, and 405 can beexpressed as k*(1/jw), and filter signals of a certain frequency. In theexemplary embodiment, a decision on whether to filter a low frequency, ahigh frequency, or a certain frequency depends on how the filteringdevices 401, 403, and 405 are disposed and connected. Also, when thereset signal S_RESET outputted from the defect detection unit 301 ofFIG. 3 is applied to the filtering devices 401, 403, and 405, thehigh-frequency signal components stored in the filtering device 401,403, and 405 are reset to 0 or a predetermined offset value. Asdescribed above, because the high-frequency signal components are allreset to 0 or the predetermined offset value, the output of thehigh-frequency gain filter 312 can be outputted while the high-frequencysignal components are being controlled.

The high-frequency gain filter 312 illustrated in FIG. 4A is constructedas a BPF. Even when the same frequency is bandpass filtered, theconstitutions and connections of the filtering devices 401, 403, and 405may vary based on filter design principles. In other words, theconstitutions and connections of the high-frequency gain filter 312 arenot limited to what is shown and may vary based on a filter design andspecifications.

A response characteristic of the high frequency gain filter 312 of FIG.4A can be defined by Equation 1 below.

$\begin{matrix}{{H(Z)} = {\frac{{K\; 11} + {K\; 12 \times Z^{- 1}}}{1 - {K\; 13 \times Z^{- 1}}} \times \frac{1 + {K\; 14 \times Z^{- 1}}}{1 - {K\; 15 \times Z^{- 1}}} \times ( {{K\; 16} + {K\; 17 \times Z^{- 1}}} ) \times {Kfg} \times 2^{6}}} & (1)\end{matrix}$

Here, H(Z) denotes the response characteristic of the high-frequencygain filter 312. K11 through K17 respectively denote amplifying rate(amplifying gain) of the amplifiers 421 through 427. Also, Z⁻¹ denotesthe filtering devices 401, 403, and 405 in the high-frequency gainfilter 312. As described above, Z⁻¹ has the value of k*(1/jw).

In this exemplary embodiment, k is an invariable number determined basedon filter design, and j is an imaginary number. Also, w is 2*pi*f,(where pi is an irrational number and f is frequency in Hz). The valueof 2⁶ in Equation 1 is for moving a cipher of the responsecharacteristic H(Z). Hence, by including a shift resister (not shown),the desired cipher can be obtained. Accordingly, the value multiplied atthe end of Equation 1 for moving the cipher of the responsecharacteristic H(Z) can be changed according to the user.

The obtaining of the response characteristic from the high-frequencygain filter 312 of FIG. 4A is well known to one of ordinary skill in therelated filter art and, thus, detailed descriptions thereof will beomitted.

FIG. 4B is a diagram illustrating the low-frequency gain filter 314illustrated in FIG. 3 in detail, according to an exemplary embodiment ofthe present invention.

Just as in the high-frequency gain filter 312, the low-frequency gainfilter 314 includes a plurality of filtering devices 451 and 453, aplurality of adders 461, 463, 465, and 467, and a plurality ofamplifiers 471. As in the high-frequency gain filter 312, a constitutionof the low-frequency gain filter 314 can vary based on filter designprinciples, and is not limited to the one shown.

FIG. 4C is a diagram illustrating signals outputted from the apparatus300, as illustrated in FIG. 3, for processing a defect, according to anexemplary embodiment of the present invention.

In the apparatus 300 according to an exemplary embodiment of the presentinvention, the reset signal S_RESET is outputted during the tracksection a to b in order to remove the high-frequency signal componentsin the high-frequency gain filter 312 or reset the high-frequency signalcomponents in the high-frequency gain filter 312 to the predeterminedoffset value. Accordingly, a distortion in the high-frequency componentsignals affected by the defect in the disc can be prevented and only alow-frequency component signal at the point at which the defect occursis outputted.

The FE signal or the TE signal is outputted from the main filter 310after the discontinuous points 256 and 258 illustrated in FIG. 2B areremoved. Accordingly, the peaking phenomenon generated in the FRO signalor the TRO signal is removed.

As described above, the apparatus for processing a defect in the opticaldisc apparatus according to an exemplary embodiment of the presentinvention resets the signal values of the high-frequency component inthe focus/tracking main filter to 0 or to a predetermined offset valuein order to remove the peaking phenomenon of the FRO signal or the TROsignal. Moreover, by removing the peaking phenomenon, an accurate servofilter characteristic can be obtained.

Also, the apparatus for processing a defect in the optical discapparatus does not include a DC hold filter, which is employed in theconventional apparatus for processing a defect and, thus, a constitutionof the apparatus for processing a defect is simplified.

While the present invention has been particularly shown and describedwith reference to exemplary embodiments thereof, it will be understoodby one of ordinary skill in the art that various changes in form anddetails may be made therein without departing from the spirit and scopeof the present invention, as defined by the following claims.

1. An apparatus for processing a defect, the apparatus comprising: amain filter; a defect detection unit that detects a defect in a disc,and when the defect is detected, outputs a reset signal to the mainfilter; wherein the main filter receives a focus error signal or atracking error signal, which are digital signals, and outputs a focusregulation signal or a tracking regulation signal to regulate a focus ora tracking location by filtering the focus error signal or the trackingerror signal, wherein the reset signal resets signal values of ahigh-frequency component existing in the main filter to
 0. 2. Theapparatus of claim 1, wherein the main filter resets the signal valuesof the high-frequency component to 0 when the reset signal is appliedthereto, and outputs the focus regulation signal or the trackingregulation signal after removing the high-frequency component of thefocus error signal or the tracking error signal.
 3. The apparatus ofclaim 2, wherein the main filter comprises: a high frequency gain filterthat filters the focus error signal or the tracking error signal to havea high-frequency gain and then outputs the filtered focus error signalor the filtered tracking error signal; a low frequency gain filter thatfilters the focus error signal or the tracking error signal to have alow-frequency gain and then outputs the filtered focus error signal orthe filtered tracking error signal; and an adder that outputs the focusregulation signal or the tracking regulation signal by adding an outputof the high-frequency gain filter and an output of the low-frequencygain filter.
 4. The apparatus of claim 3, wherein the high-frequencygain filter operates in response to the reset signal when the defect isdetected, and initializes signal values of the high-frequency componentexisting in the high-frequency gain filter to 0 when the reset signal isapplied.
 5. The apparatus of claim 2, further comprising a digital toanalog converter that receives the focus regulation signal or thetracking regulation signal from the main filter and then outputs thefocus regulation signal or the tracking regulation signal afterconverting the focus regulation signal or the tracking regulation signalto an analog signal.
 6. The apparatus of claim 3, wherein thelow-frequency gain filter filters the low-frequency component of thefocus regulation signal or the tracking regulation signal, and controlsthe received focus regulation signal or the tracking regulation signalto pass only a low-frequency component of the focus error signal or thetracking error signal.
 7. The apparatus of claim 5, further comprisingan analog to digital converter that is connected to a front terminal ofthe main filter and converts the focus error signal and the trackingerror signal generated as analog signals to digital signals beforeoutputting the focus error signal and the tracking error signal.
 8. Anapparatus for processing a defect, the apparatus comprising: a mainfilter; a defect detection unit that detects a presence of a defect in adisc and outputs a reset signal to the main filter when the defect isdetected; and the main filter receives a focus error signal or atracking error signal, which are digital signals, and outputs a focusregulation signal or a tracking regulation signal to regulate a focus ora tracking location by filtering the focus error signal or the trackingerror signal, wherein the reset signal resets the signal values of ahigh-frequency component existing in the main filter to a predeterminedoffset value.
 9. The apparatus of claim 8, wherein the predeterminedoffset value is a value, that offsets the signal values of thehigh-frequency component existing in the main filter to be fixed to auniform value and is specified by a user.
 10. The apparatus of claim 9,wherein the main filter resets an output value of the high-frequencycomponent existing in the main filter to have the offset value when thereset signal is applied, and outputs the focus error signal or thetracking error signal after removing the high-frequency component of thefocus error signal or the tracking error signal, leaving the offsetvalue.
 11. The apparatus of claim 9, wherein the main filter comprises:a high-frequency gain filter that filters the focus error signal or thetracking error signal to have a high-frequency gain and then outputs thefiltered focus error signal or the filtered tracking error signal; alow-frequency gain filter that filters the focus error signal or thetracking error signal to have a low-frequency gain and then outputs thefiltered focus error signal or the filtered tracking error signal; andan adder that outputs the focus regulation signal or the trackingregulation signal by adding an output of the high-frequency gain filterand an output of the low-frequency gain filter.
 12. The apparatus ofclaim 11, wherein the high-frequency gain filter operates in response tothe reset signal when the defect is detected and initializes the signalvalues of the high-frequency component existing in the main filter tothe offset value when the reset signal is applied.
 13. The apparatus ofclaim 9, further comprising a digital to analog converter that receivesthe focus regulation signal or the tracking regulation signal from themain filter and then outputs the focus regulation signal or the trackingregulation signal after converting the focus regulation signal or thetracking regulation signal to an analog signal.
 14. The apparatus ofclaim 9, wherein the low-frequency gain filter filters the low-frequencycomponent of the focus regulation signal or the tracking regulationsignal and controls the received focus regulation signal or the trackingregulation signal to to pass only a low-frequency component of the focuserror signal or the tracking error signal.
 15. The apparatus of claim13, further comprising an analog to digital converter that is connectedto a front terminal of the main filter and converts the focus errorsignal and the tracking error signal generated as analog signals todigital signals before outputting the focus error signal and thetracking error signal.